Resources
Heartwood
Heartwood is a resource.
How to get
Buy it from the Wood Store vendor for 20 Bucks. Find it as loot, most reliably from Resource Node Wood Log Chunk Rare Wood.
Extra strong, this wood from the core of trees is important for crafting high end weapons and tools. Collected by milling logs or splitting them with Tier 2 or higher axes.
In-game descriptions are still being filled in by the developers, so a few may be placeholder text or may not match the item yet.